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/*
* pam authentication module that can be pointed at any username/crypted
* text file so that pam using application can use an alternate set of
* passwords than specified in system password database
*
* Copyright (c) 1999-2003 Charl P. Botha <cpbotha@cpbotha.net>
* Copyright (c) 2012-2013 Timo Weingärtner <timo@tiwe.de>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, and the entire permission notice in its entirety,
* including the disclaimer of warranties.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* ALTERNATIVELY, this product may be distributed under the terms of the
* GNU General Public License, in which case the provisions of the GPL are
* required INSTEAD OF the above restrictions. (This clause is
* necessary due to a potential bad interaction between the GPL and
* the restrictions contained in a BSD-style copyright.)
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifdef USE_CRYPT_R
#define _GNU_SOURCE
#include <crypt.h>
#else
#ifndef _XOPEN_SOURCE
#define _XOPEN_SOURCE 700
#endif
#ifndef _BSD_SOURCE
#define _BSD_SOURCE
#endif
#endif
#include <syslog.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/file.h>
#include <unistd.h>
#include <syslog.h>
#include <security/pam_appl.h>
#define PAM_SM_AUTH
#include <security/pam_modules.h>
#include <security/pam_ext.h>
static int lock_fd(int fd) {
int delay;
for (delay = 5; delay <= 40; delay *= 2) {
if (flock(fd, LOCK_SH | LOCK_NB) == -1) {
/* failed */
if (errno != EWOULDBLOCK) goto failed;
sleep(delay);
}else{
return 0;
}
}
if (flock(fd, LOCK_SH | LOCK_NB) != -1) return 0;
failed:
return -1;
}
/* expected hook for auth service */
__attribute__((visibility("default")))
PAM_EXTERN int pam_sm_authenticate(pam_handle_t *pamh, int flags,
int argc, const char **argv) {
int i;
const char *name;
char const * password;
char const * pwdfilename = NULL;
char const * stored_crypted_password = NULL;
char const * crypted_password;
FILE *pwdfile;
int use_flock = 0;
int use_delay = 1;
int debug = 0;
char * linebuf = NULL;
size_t linebuflen;
#ifdef USE_CRYPT_R
struct crypt_data crypt_buf;
#endif
/* we require the pwdfile switch and argument to be present, else we don't work */
for (i = 0; i < argc; ++i) {
if (!strcmp(argv[i], "pwdfile") && i + 1 < argc)
pwdfilename = argv[++i];
else if (!strncmp(argv[i], "pwdfile=", strlen("pwdfile=")))
pwdfilename = argv[i] + strlen("pwdfile=");
else if (!strcmp(argv[i], "flock"))
use_flock = 1;
else if (!strcmp(argv[i], "noflock"))
use_flock = 0;
else if (!strcmp(argv[i], "nodelay"))
use_delay = 0;
else if (!strcmp(argv[i], "debug"))
debug = 1;
}
#ifdef HAVE_PAM_FAIL_DELAY
if (use_delay) {
if (debug) pam_syslog(pamh, LOG_DEBUG, "setting fail delay");
(void) pam_fail_delay(pamh, 2000000); /* 2 sec */
}
#endif
if (!pwdfilename) {
pam_syslog(pamh, LOG_ERR, "password file name not specified");
return PAM_AUTHINFO_UNAVAIL;
}
if (pam_get_user(pamh, &name, NULL) != PAM_SUCCESS) {
pam_syslog(pamh, LOG_ERR, "couldn't get username from PAM stack");
return PAM_AUTH_ERR;
}
if (debug) pam_syslog(pamh, LOG_DEBUG, "username is %s", name);
if (!(pwdfile = fopen(pwdfilename, "r"))) {
pam_syslog(pamh, LOG_ALERT, "couldn't open password file %s", pwdfilename);
return PAM_AUTHINFO_UNAVAIL;
}
if (use_flock && lock_fd(fileno(pwdfile)) == -1) {
pam_syslog(pamh, LOG_ALERT, "couldn't lock password file %s", pwdfilename);
fclose(pwdfile);
return PAM_AUTHINFO_UNAVAIL;
}
/* get the crypted password corresponding to this user out of pwdfile */
while (getline(&linebuf, &linebuflen, pwdfile) > 0) {
/* strsep changes its argument, make a copy */
char * nexttok = linebuf;
/* first field: username */
char * curtok = strsep(&nexttok, ":");
/* skip non-matching usernames */
if (strcmp(curtok, name))
continue;
/* second field: password (until next colon or newline) */
if ((curtok = strsep(&nexttok, ":\n"))) {
stored_crypted_password = curtok;
break;
}
}
fclose(pwdfile);
/* we keep linebuf (allocated by getline), stored_crypted_password is pointing into it */
if (!stored_crypted_password)
if (debug) pam_syslog(pamh, LOG_ERR, "user not found in password database");
if (stored_crypted_password && !strlen(stored_crypted_password)) {
if (debug) pam_syslog(pamh, LOG_DEBUG, "user has empty password field");
free(linebuf);
return flags & PAM_DISALLOW_NULL_AUTHTOK ? PAM_AUTH_ERR : PAM_SUCCESS;
}
if (pam_get_authtok(pamh, PAM_AUTHTOK, &password, NULL) != PAM_SUCCESS) {
pam_syslog(pamh, LOG_ERR, "couldn't get password from PAM stack");
free(linebuf);
return PAM_AUTH_ERR;
}
if (!stored_crypted_password) {
free(linebuf);
return PAM_USER_UNKNOWN;
}
if (debug) pam_syslog(pamh, LOG_DEBUG, "got crypted password == '%s'", stored_crypted_password);
#ifdef USE_CRYPT_R
crypt_buf.initialized = 0;
if (!(crypted_password = crypt_r(password, stored_crypted_password, &crypt_buf)))
#else
if (!(crypted_password = crypt(password, stored_crypted_password)))
#endif
{
pam_syslog(pamh, LOG_ERR, "crypt() failed");
free(linebuf);
return PAM_AUTH_ERR;
}
if (strcmp(crypted_password, stored_crypted_password)) {
pam_syslog(pamh, LOG_NOTICE, "wrong password for user %s", name);
free(linebuf);
return PAM_AUTH_ERR;
}
if (debug) pam_syslog(pamh, LOG_DEBUG, "passwords match");
free(linebuf);
return PAM_SUCCESS;
}
/* another expected hook */
__attribute__((visibility("default")))
PAM_EXTERN int pam_sm_setcred(pam_handle_t *pamh, int flags,
int argc, const char **argv)
{
return PAM_SUCCESS;
}
#ifdef PAM_STATIC
struct pam_module _pam_listfile_modstruct = {
"pam_pwdfile",
pam_sm_authenticate,
pam_sm_setcred,
NULL,
NULL,
NULL,
NULL,
};
#endif
/* vim:set ts=8 sw=4: */
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